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Lecture-8-Introducti_38192

Lecture-8-Introducti_38192 - Ancellsmetabolism...

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An cell’s metabolism consists of 1000’s of chemical reactions Introduction to Metabolism An cell s consists of 1000 s of chemical reactions catalyzed by enzymes & organized into a myriad of metabolic pathways . Each pathway has this form : Larger complex organic molecules Metabolism manages the material & energy resources of the cell: Larger, complex organic molecules Synthesis via anabolic pathways Breakdown via catabolic pathways which are… energy which are… Example: Example: …energy releasing …energy requiring cellular respiration dehydration reactions f Simpler organic molecules Use to form ATP’s Uses ATP’s
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Energy Cells require energy to do work: biosynthesis, transport of molecules, cellular movements, etc. Energy forms: kinetic, thermal (heat), potential Potential energy: energy matter possesses due to its’ position or structure; e.g., arrangement of atoms in a molecule Chemical energy: potential energy stored in chemical bonds A cell’s metabolism does not create energy, rather it transforms energy from one form to another. How? More potential h Potential to kinetic energy energy here… …than down here Convert kinetic to potential energy (walking up stairs)
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The energy transformations that occur within cells is studied Thermodynamics 101 using thermodynamics . Cells are open systems : exchange matter/energy with its surroundings ( closed systems cannot) 1 st Law: energy cannot be created or destroyed, it is transferred & t f d & transformed. Energy lost as heat Chemical energy F i f Kinetic energy Formation of breakdown products 2 nd Law: during energy conversion, a portion of this energy is unusable and lost as heat (No process is 100% efficient). Loss of usable energy = increases the entropy (disorder) of the surroundings
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Free Energy Spontaneous processes occur without an input of energy; they increase the entropy [example: concentrated dye randomly disperses in solution] . Non spontaneous process requires energy input to proceed; decrease entropy. Whether reactions are spontaneous or not relies on assessing the energy & entropy changes in the system & surroundings. For us, a system = chemical reaction, can define as follows: Total energy = usable energy + T x unusable energy T x unusable energy enthalpy (H) free energy (G) entropy (S) = + T =temperature (in Kelvin K) T =temperature (in Kelvin, K) Free energy (G) can perform work; the value of G determines whether a process is spontaneous or not whether a process is spontaneous or not. Δ G = Δ H – T Δ S
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Free energy changes: Δ G = Δ H – T Δ S negative Δ G : ( Δ G <0) = spontaneous; H decreases; TS increases positive Δ G : ( Δ G 0) = non spontaneous; H increases; TS decreases Δ G can be viewed in terms of free energy for the final & initial state of a process: Δ G = G final G initial Negative G: loss of free energy from initial to final state; measure of stability Æ change from unstable to more stable state: Initial state Final state
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An exergonic reaction : a net
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